Study of genetic diseases with neoplastic manifestations and detailed investigations of families at high risk of cancer may help detect environmental and genetic influences in carcinogenesis, especially when appropriate laboratory assays are used, and may lead to important opportunities for cancer control. Neurofibromatosis, an autosomal dominant disorder with a large predisposition to cancer, was tentatively linked to the serum protein marker, GC, on chromosome 4, by classical genetic linkage analysis in five families with a lod score of 2.2; because a sixth family gave a negative lod score, genetic heterogeneity may be present in this common but understudied preneoplastic disorder. Prophase karyotypes on 14 neurofibromatosis patients were normal. A family with the Saethre-Chotzen syndrome, an autosomal dominant trait with craniosynostosis, had two brothers with Hodgkin's disease, another with testicular carcinoma, and a sister with nasopharyngeal carcinoma; intensive laboratory investigation revealed subclinical immune dysfunction. Analytic studies documented an excess of urogenital malformations in patients with Ewing's sarcoma, a tumor of uncertain origins with a characteristic chromosomal translocation. Formal genetic analysis failed to support the clinical impression of autosomal dominant inheritance of hypertrophic cardiomyopathy, an often familial hyperplasia of interventricular septum. Cytogenetic abnormalities associated with human cancer were summarized in a figure that emphasized the genes assigned to specific chromosomes, including the newly described human oncogenes. Other literature reviews, guest lectures, and committee activities were done to stimulate similar research in the metropolitan Washington area and worldwide.